1. Field of the Invention
The present invention relates to a method of holding a workpiece to be worked precisely, and more particularly to a method of holding and publishing a workpiece on a workpiece holder of a driving member or the like for driving the workpiece, through utilization of freezing a material such as water or the like so that the workpiece can be securely retained on the holder while being worked in a grinding liquid.
2. Description of the Prior Art
Conventionally, for example, in the case of working of both surfaces of a silicon wafer with high precision, each surface of the wafer is held to a supporting surface or the like of a driving member through using organic adhesive.
In this case, however, the organic adhesive must have a certain thickness since too small a thickness of the adhesive may lead to loss of its adhesion due to limitation of its molecular structure and, in addition, since the adhesive is soft until it is hardened, the wafer cannot be held with its adhereing surface completely parallel to the supporting surface or the like. Therefore, the use of the adhesive poses a problem in terms of working precision. Moreover, the adhesive is hard to be peeled off and the wafer may be often damaged when peeling off the adhesive; this imposes limitations on machining of a large sized wafer. Furthermore, the adhesive is generally hardened by heating; however, this heat treatment causes thermal expansion of the air or other substances included in the adhesive. This also presents the problem that an extra stress may be applied to the wafer due to the difference in thermal expansion between the material of the wafer supporting surface or the like and the wafer.